jQuery Grid Plugin - jqGrid

Hi,
My code is like below;
….
<ClientSideEvents AfterEditDialogShown="populateFields" AfterAddDialogShown="populateFields" />
….

<script type="text/javascript">
// This function gets called whenever an add/edit dialog is opened
 function populateFields() {
  $("#FieldName")
   .html("<option value=''>Loading objects...</option>")
                        .attr("disabled", "disabled");

  $.ajax({
                 url: document.URL + "?drp=drpField",
                        type: "GET",
                        cache: false,
                        success: function (objectHtml) {
                        $("#FieldName")
                         .removeAttr("disabled")
                                .html(objectHtml);
   }
  });
 }
</script>

Here in javascript I need to pass primary row id of the parent grid.

Thanks in advance.